Not receiving needed mental health treatment is a major problem for vulnerable low-income young adults. This three-year study of approximately 11,000 young adults (ages 18 to 26 years old) who were enrolled in the Medicaid program from 2004 to 2005 and were authorized for extended use of mental health services will provide a comprehensive description of their utilization of inpatient and outpatient mental health services, use of psychotropic medications, and mental health treatment costs over a period of 18-months in length. The study will focus on understanding the particular roles of Medicaid insurance continuity (i.e., periods without lapses in coverage) and access to primary care services in enabling mental health treatment. A new framework that may clarify the complex relationships among insurance continuity, access to primary care services, and use of mental health services during the early years of adulthood will be examined in relation to two specific aims. First, we will examine how Medicaid/SCHIP coverage continuity and other indicators of access to primary care services during the past year are related to differences in these young adults'utilization of primary care services, utilization and costs of outpatient and inpatient mental health services, and utilization and costs of psychotropic medications over the subsequent 6-, 12-, and 18-months. Our second aim is to characterize how their utilization of primary care services and their utilization of outpatient and inpatient mental health services and psychotropic medications during a 6- month period of continuous Medicaid/SCHIP enrollment relate to their subsequent likelihood of disenrollment from Medicaid/SCHIP. Data needed to accomplish these aims will be assembled into a unique database that will contain information from a Medicaid/SCHIP information system and from a public MH system information system. These data will allow us to examine use of primary care and mental health services, as well treatment costs and Medicaid disenrollment over a 1 1/2 year period. By providing information about the impacts of Medicaid enrollment patterns on vulnerable young adults'access to mental health services during the period of transition into adult-oriented healthcare systems, and by providing information about the correlates of disenrollment from Medicaid, our research will inform policy reforms in the Medicaid program.